Conversion of hydrocarbon oils



March 1, 1938. ,J B

CONVERSION OF HYDROCARBON OILS Original Filed July 18, 1934 FRACTIONATOR SEPARATING CHAMBER FURNACE FURNACE 2O FURNACE INVENTOR JACOB BENJAMIN HEID v A%ZIEY Patented Mar. 1, 1938 UNITED STATES CONVERSION OF HYDROCARBON OILS Jacob Benjamin Heid, Chicago,

Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application July 18, 1934, Serial No. 735,752 Renewed November 20, 1935 10 Claims.

This invention is related to an improved process for the selective conversion of relatively lowboiling and high-boiling hydrocarbon oils wherein quick separation is effected between the liquid and vaporous products resulting from conversion of the relatively heavy oils, the vaporous products subjected to continued conversion, the liquid products subjected to further vaporization, the residual liquid resulting from said further vaporization subjected to coking and the highly heated products resulting from conversion of the relatively low-boiling oils utilized as the heat carrying medium to assist the coking operation.

In one specific embodiment, the invention comprises subjecting a hydrocarbon oil of relatively high-boiling characteristics to conversion temperature at superatmospheric pressure in the heating coil, introducing the heated products into a separating chamber also operated at substantial superatmospheric pressure wherein vaporous and liquid conversion products are quickly separated, subjecting the vaporous products from said separating chamber to continued conversion in a reaction chamber operated at substantial superatmospheric pressure, introducing the products from said reaction chamber into a fractionator wherein their desirable low-boiling components are separated, as fractionated vapors, 30 from their higher boiling insufiiciently converted components, which latter are condensed as reflux condensate, separating the reflux condensate into selected relatively low-boiling and high-boiling fractions, subjecting the relatively high-boil- 35 ing fraction to said conversion, subjecting the fractionated vapors to condensation, recovering the resulting distillate, withdrawing the liquid conversion products from said separating chamber, introducing the same into a reduced pres- 40 sure vaporizing chamber, subjecting vapors evolved in the vaporizing chamber to said fractionation, withdrawing non-vaporous residual liquid from the vaporizing chamber and subjecting the same to coking in a low pressure coking zone, subjecting the relatively low-boiling fractions of the reflux condensate to more severe conversion conditions of elevated temperature and superatmospheric pressure in a separate heating coil, introducing the resulting highly heated products into direct contact with the residual materials undergoing coking for the purpose of assisting their reduction to coke and subjecting vaporous products of the coking operation to said fractionation.

Several modifications of the operation above outlined may be employed without departing from the scope of the present invention. For example, the hydrocarbon oil charging stock for the process, depending upon its characteristics, may be subjected to conversion, together with either the low-boiling or the high-boiling fractions of the reflux condensate, or may be supplied to the fractionator for separation into selected relatively low-boiling and high-boiling fractions and subjected to conversion together with the corresponding fractions of the reflux, condensate or, when desired, it may be independently subjected to conversion in a separate heating coil, the products from which are discharged into the separating chamber.

I am aware that the present process involves various steps which are not novel in themselves and that even some of the combinations of steps employed are not new with the present invention. The invention is directed to the novel and advantageous combination of a method and means for quickly separating vaporous and liquid conversion products resulting from the conversion of relatively high-boiling oils accompanied by continued conversion of the vapors at elevated temperature and superatmospheric pressure, vaporization of the liquid conversion products at substantially reduced pressure and coking of the resulting residual liquid with the assistance of highly heated relatively low-boiling oils from within the system. It will be apparent that there is a definite cooperation between these various steps of the process and that they mutually contribute to produce the desired final results.

The accompanying diagrammatic drawing illustrates one specific form of apparatus in which the invention may be carried out. Referring to the drawing, hydrocarbon oil charging stock for the process, which may be any desired type of oil, is supplied through line I and valve 2 to pump 3 by means of which it is fed through line 4 and may be directed, all or in part, either through line 5 and valve 6 into fractionator l or through line 8, valve 9 and line I 0 to heating coil II or from line 8 through lines l2 and I3, valve l4 and line l5 to heating coil IE or from line l2 through line I l and valve I8 into heating coil IS. The method of supplying the charging stock to the process will depend, primarily, upon its characteristics, for example, when the charging stock is an oil of relatively low-boiling characteristics it is preferably supplied to heating coil II or if of relatively high-boiling characteristics it is preferably supplied'to heating coil Hi. If, on the other hand, the charging stock is an oil of relatively wide boiling range it is preferably supplied to the fractionator and is separated, together with the insufliciently converted intermediate products of the process, as will be later more fully described, into selected relatively low-boiling and high-boiling fractions which are respectively subjected to separate conversion in heating coils ll and 16. Whether the charging stock is of lowboiling or high-boiling characteristics or of relatively wide boiling range it is within the scope of the invention to supply it, all or in part, to fractionator I except in case it contains low-boiling fractions of inferior quality within the boiling range of the desired light distillate product of the process. Since this'product is removed as the overheat stream from fractionator I and such materials in the charging stock would contaminate the product if fed to the fractionator. The present invention also provides for separate treatment of the charging stock without mixing the same with either the low-boiling or high-boiling fractions of the reflux condensate. This method of operation may be accomplished, when desired, by passing the charging stock, as previously described, to heating coil l9 and is particularly desirable in case the charging stock is an intermediate oil such as, for example, gas oil or the like of lower boiling nature than the reflux condensate supplied to heating coil I6 and of higher boiling nature than the reflux condensate supplied to heating coil ll, although separate conversion of the charging'stock, regardless of its nature; is within the scope of the invention.

When the charging stock is supplied to heating coil l9 it is subjected therein to the desired conversion temperature, preferably at a substantial superatmospheric pressure, by means of heat supplied from furnace 2B of any suitable form. The heated oil is discharged from heating coil 19 through line 2|, valve 22 and line 23 into separating chamber 24.

Relatively high-boiling fractions of the reflux condensate formed in fractionator '1 are supplied, as will be later more fully described, either alone or together with the charging stock or high-boiling fractions thereof, to heating coil l6 and the oil passing through this zone is heated to the desired conversion temperature by means of heat supplied from any suitable form of furnace 25. The stream of heated materials are discharged from heating coil l6 preferably at substantial superatmospheric pressure through line 23 and valve 26 into separating chamber 24.

Heating coils l6 and 19 may be operated at substantially the same or under different pressure conditions and preferably the pressure employed in separating chamber 24 is substantially the same as that at the outlet from the heating coil employing the lowest pressure. However, when desired, a somewhat reduced superatmospheric pressure relative to that employed at the outlet from the heating coils may be utilized in cham- -ber24. In the particular case here illustrated, a suitable baflie 21 is provided in chamber 24 so that the heated mixture of liquids and vapors entering this zone passes first downward on one side of the chamber to its lower portion wherein a major portion of the liquid conversion products are separated fromthe vapors, the latter passing together with the remainder of the entrained liquid in an upward direction on the opposite side of the chamber. This reversal of flow within chamber 24 serves to assist quick separation'of vaporous and liquidconversion products in this zone but is not intended as a limiting feature of "in the reaction chamber.

the invention and may be eliminated, when desired, or other suitable well known means of assisting separation may be substituted therefor. The liquids separated from the vaporous conversion products in chamber 24 are withdrawn from the lower portion of this zone through line 28 and valve 29 and are introduced into vaporizing chamber 39. The remainder of the conversion products supplied to chamber 24, which are predominantly vapors, are withdrawn from the upper portion of this. zone through line 3! and .valve 32 andare introduced into reaction chamber 33.

It will be noted in connection with separating chamber 24 and reaction chamber 33 that in the present invention the usual sequence of these zones is reversed and that instead of employing substantially reduced pressure in the vaporizing chamber relative to that employed in the reaction chamber, both zones are operated at sub stantially the same relatively high superatmospheric pressure. The arrangement and method of operation of chambers 24 and 33, as provided by the present invention, offers distinct advantages over the conventional method wherein a high pressure reaction chamber is followed by a reduced pressure vaporizing and separating chamber, particularly in conjunction with the other features of the present invention. The use of high superatmospheric pressure in the separating chamber precludes any substantial vaporization in this zone and permits quicker and more complete separation of vaporous and liquid products than when their separation is attempted at substantially reduced pressure. The use of a separating chamber ahead of the reaction chamber also precludes any excessive further conversion of residual liquid products, which is often the case when the entire stream of heated products from the heating coil is passed through a relatively large high-pressure reaction chamber before liquid and vaporous products are separated, and since, in the present invention, the liquid conversion products are quickly separated from the stream of heated products from the heating coils without being subjected to continued conversion time in the reaction chamber, more severe conversion conditions may be employed in the heating coils than could be otherwise safely employed without the danger of excessive coke and gas formation from excessive conversion of the residual liquid. However, the use of a high-pressure reaction chamber, such as chamber 33, following the separating zone insures continued conversion of the vaporous products to the desired degree. The use of more se vere conversion conditions in the heating coils favors the production of motor fuel of higher antiknock value, particularly in conjunction with continued conversion of the vaporous products Particular attention is directed to the fact that without the steps provided by the present invention, which will be later described in more detail, for further treatment of the liquid conversion products following their removal from the separating chamber, the use of a high-pressure separating chamber ahead of the reaction chamber would not be desirable since the liquid removed by such high-pressure reaction chamber contains in addition to heavy residue, lower boiling components which are desirable as crackingstock. If the liquid conversion products from-chamber 24 were removed from the system without adequate further treatment their desirable lower'boiling components could not be returned, as provided by the present invention, to further conversion within the system and the yield of the desired light distillate product would be materially reduced.

Chamber 33, as already indicated, is preferably operated at substantially the same pressure as that employed in chamber 24 and the hot conversion products supplied to this zone, as previously described, are subjected during their passage therethrough to continued conversion for a predetermined time. The resulting products are discharged, in the case here illustrated, from the lower portion of chamber 33 through line 34 and valve 35 into fractionator and it is within the scope of the invention, although not illustrated, to cool the products discharged from the reaction chamber sufficiently to retard or arrest their further conversion in order to prevent their excessive conversion and to preclude the appreciable formation and deposition of coke or heavy residual materials such as tar and the like in line 34. This may be accomplished, for example, by indirect cooling of the material leaving chamber 33 in any suitable well known manner, not illustrated, or by directly commingling with these materials in the lower portion of chamber 33 on in line 34 suitable cooling oil such as, for example, charging stock and/or a regulated portion or selected fractions of the reflux condensate formed in fractionator 7. These features are not new except in combination with the other features of the invention and for the sake of simplicity are not illustrated.

The vaporous products supplied to fractionator 1 (including the conversion products from reaction chamber 33 and other vaporous products supplied to this zone, as will be later more fully described) are subjected to fractionation therein for the separation of their low-boiling components from their insufiiciently converted higher boiling components, which latter are condensed in the fractionator as reflux condensate. The fractionated vapors of the desired end-boiling point, which comprise the desired low-boiling product of the process, such as, for example, good quality motor fuel, are withdrawn together with uncondensable gas produced by the process from the upper portion of f-ractionator 7 through line 36 and valve 31 tobe subjected to condensation and cooling in condenser 38. The resulting distillate and gas passes through line 39 and valve 40 to collection and separation in receiver 4|. Uncondensable gas may be released from the receiver through line 42 and valve 43. The distillate may be withdrawn from receiver 4| through line 44 and valve 45 to storage or to any desired further treatment. When desired, a regulated portion of the distillate collected in receiver 4| may be recirculated by well known means, not illustrated, to the upper portion of fractionator 1 to serve as a cooling and refluxing medium to assist fractionation of the vapors in this zone and to maintain the desired vapor outlet temperature.

In accordance with the features of the present invention, the reflux condensate formed in fractionator is separated by fractional distillation in this zone into selected relatively low-boiling and high-boiling fractions. The high-boiling fractions are withdrawn from the lower portion of the fractionator through line 46 and valve 4'! to pump 48 by means of which they are returned through line I5 and valve 49 to heating coil i6 for further conversion, as already described. The selected relatively low-boiling fractions of the reflux condensate may be withdrawn from one or a plurality of suitable intermediate points in fractionator and pass, for example, through line 50 and valve 5| to pump 52 by means of which they are supplied through line 53, valve 54 and line ID to heating coil II for further conversion, either alone or together with hydrocarbon oil charging stock for the process, which may be supplied to this zone, when desired, as previously described.

Chamber 30 is preferably operated at a sub stantially reduced pressure relative to that employed in chamber 24 by means of which the liquid conversion products supplied to this zone from chamber 24, as previously described, are subjected to appreciable further vaporization for the purpose of separating the heavy high cokeiocrming components of the liquid conversion products from their lower boiling components which may be successfully subjected to further conversion within the system for the production of additional yields of desirable low-boiling materials. The vapors evolved from chamber 30 are withdrawn therefrom through line 5| and valve 62 and are directed through line 63 to fractionation in fractionator 1. The residual liquid conversion products remaining unvaporized in chamber 36' are withdrawn from the lower portion of this zone through line 64 and a regulated portion thereof may, when desired, be (iirected through valve 65 in this line to cooling and storage or elsewhere, as desired. However, a regulated portion or all of the residual liquid withdrawn from chamber 30 is subjected to coking within the system and in the cas'e here illustrated residual liquid may be diverted from line 64 through line 56 and valve 6? to pump 68 by means of which it is fed through line 69 and,

let from heating coil i and the stream of highly.

heated products are discharged from this zone through line 56 and valve 51. Preferably, in case a high superatmospheric pressure is employed in heating coil i, the pressure imposed upon the stream of highly heated oil leaving this zone is substantially reduced as it passes through valve 51 so that it may be introduced into coking chamber 60, which is preferably operated at substantially atmospheric or relatively low superatmospheric pressure. The stream of highly heated products from heating coil may be introduced into the coking chamber at any desired point in this zone, a plurality of suitable lines 53 controlled by valves 59 being provided in the case here illustrated for this purpose. Preferably, this material is either introduced into direct contact with the materials undergoing coking in chamber Si! or is commingled, prior to its intro-- duction into the coking chamber, with the residual liquid from chamber 35 suppliedto this zone, in which latter case the commingled materials may also be introduced into the coking chamber through any or all of the various lines 58 controlled by valves 59.

The coke produced in chamber 60 may be allowed to accumulate within this zone tobe r emoved therefrom after the operation of the chamber is completed and, when desired, a plurality of coking chambers similar to chamber 60, but not illustrated, may be employed and may be simultaneously operated or, preferably, are alternately operated, cleaned and prepared for further operation so that the duration of the operating cycle of the process is not limited by the capacity of the coking chamber. Chamber 6!! is provided with a suitable drain-line H controlled by valve 12 which may also serve as a means of introducing steam, water or any other suitable cooling medium into the chamber after its operation is completed and after it has been isolated from the rest of the system in order to hasten cooling and facilitate cleaning of the chamber. The vaporous products of the coking operation are withdrawn from the upper portion of chamber 60 through line '53 and may be directed through line 63 and valve H! to fractionation in fractionator 1. However, the vaporous products from the coking zone will normally contain a certain amount of entrained particles of high coke-forming materials such as tars, pitches and the like and in order to separate these materials from the vapors, prior to their introduction into the fractionator, the vapors from coking chamber 60 are preferably directed through valve 15 in line 13 into chamber 30.

Suitable fractionating means or baffles of any desired form may, when desired, be provided in the upper portion of chamber 30 to assist in affecting relatively clean separation of vaporous and residual liquid products in this zone. By means of the method of operation just described in a relatively heavy high coke-forming component of the vaporous products from the coking zone are collected in chamber 30, together with the residual liquid resulting from the partial vaporization in this zone of the liquid conversion products from chamber 24, and may be returned therewith to coking chamber 60 for further treatment and eventual reduction to coke, while the total vaporous products from chamber 30 are directed through line 6|, valve 62 and line 63 to fractionation in fractionator 1.

In a process of the character illustrated and above described, the preferred range of operating conditions may be approximately as follows: When a separate heating coil is employed for conversion of the charging stock the conversion conditions employed therein may vary over a relatively wide range, depending upon the nature of the charging stock, the conversion temperature measured at the outlet from the heating coil ranging, for example, from 850 to 950 F., preferably with a substantial superatmospheric pressure at this point in the system of from to 500 pounds, or more, per square inch, substantially the same range of conditions may be employed at the outlet from the heating coil to which the relatively high-boiling fractions of the reflux condensate are supplied although normally different conversion conditions are employed in each of the heating coils when both zones are utilized. The pressure employed in the separating chamber may also'range, for example, from 100 to 500 pounds, or thereabouts, per square inch, and ordinarily is approximately the same as that employed in the charging stock or heavy reflux heating coil, whichever heating coil employs the lowest pressure. However, when desired, the separating chamber may be operated at a somewhat reduced superatmospheric pressure relative to the pressures employed in both heating coils. The reaction chamber is preferably operated at substantially the same pressure as that employed in the separating chamber. The vaporizing chamber to which liquid conversion products from the separating chamber are supplied preferably employs a substantially reduced pressure relative to that employed in the separating chamber which may range, for example, from 100 pounds or thereabouts per square inch to substantially atmospheric pressiu'e. Any desired pressure within substantially this same range may be employed in the coking chamber and this zone may, when desired, utilize either a lower or higher pressure than that employed in the vaporizing chamber. The heating coil to which the relatively low-boiling fractions of the reflux condensate are supplied may utilize an outlet conversion temperature ranging, for example, from 900 to 1050 F., or thereabouts. Preferably a substantial superatmospheric pressure of the order of 300 to 1000 pounds, or thereabouts, per square inch, is employed at the outlet from the light oil heating coil, although lower pressures down to substantially atmospheric pressure may be employed in this zone, when desired. The fractionating, condensing and collecting portions of the system may employ pressure substantially the same or somewhat lower than the pressure employed in the vaporizing or coking chamber whichever employs the lowest pressure.

As a specific example of one of the many possible operations of the process of the present invention as it may be practiced in an apparatus such as illustrated and above described, the charging stock, which comprises a Mid-Continent gas oil of about 32 A. P. I. gravity, is independently subjected in the heating coil to a conversion temperature, measured at the outlet therefrom, of approximately 950 F., at a superatmospheric pressure of about 350 pounds per square inch. High-boiling fractions of the reflux condensate from the fractionator of the system, containing not over approximately 5 percent of materials boiling below 600 F., are subjected in a separate heating coil to an outlet conversion temperature of approximately 935 F., at a superatmospheric pressure of about 350 pounds per square inch and the heated products from both'the heavy reflux and raw oil heating coils are introduced into a separating chamber also maintained at a superatmospheric pressure of about 350 pounds per square inch. Substantially the same pressure is employed in the reaction chamber to which vaporous products from the separating chamber are supplied and the materials leaving the reaction chamber are cooled,

prior to, their introduction into the fractionator, V

to a temperature of approximately 760 F. Liquid conversion products are withdrawn from the separating chamber and subjected to further vaporization in a vaporizing chamber operated at a superatmospheric pressure of approximately 30 pounds per square inch. The non-vaporous residual liquid from the vaporizing chamber is directed to a coking chamber operated at a superatmospheric pressure of approximately 50 pounds per square inch. Low-boiling fractions of the reflux condensate from the fractionator of the system, having a boiling range of approximately 400 to 600 F., are subjected in a separate heating coil to a conversion temperature of approximately 970 F., at a superatmospheric pressure of about 600 pounds per square inch and the highly heated products from this zone are introduced into direct contact with the residual materials undergoing coking in the coking chamber. Vaporous'productsfrom the coking chamber are supplied to the vaporizing chamber and the vapors from the vaporizing chamber are directed to the fractionator of the system which is operated at substantially the same pressure as that employed in the vaporizing chamber. This operation may yield, per barrel of charging stock, approximately 67 percent of 400 F., end-point motor fuel having an octane number of approximately 70 and about 54 pounds of coke of substantially uniform quality, good structural strength and low volatility, the remainder is chargeable, principally, to uncondensable gas.

- I claim as my invention 1. A process for the conversion of hydrocarbon oils which comprises subjecting a relatively highboiling oil from within the systemto conversion temperature at superatmospheric pressure in a heating coil, introducing the heated products into a separating chamber also operated at substantial superatmospheric pressure wherein vaporous and liquid conversion products are quickly separated, introducing vaporous conversion products from the separating chamber into a reaction chamber, also operated at substantial superatmospheric pressure, wherein they are subjected to continued conversion, introducing the resulting products from. the reaction chamber into a fractlonator wherein they are subjected to fractionation for the separation of reflux condensate, comprising their insufliciently converted components, from their desirable lower boiling components, subjecting fractionated Vapors of the desired endboiling point to condensation, recovering the resulting distillate, withdrawing liquid conversion products from the separating chamber and introducing them into a vaporizing chamber operated at substantially reduced pressure relative to that employed in the separating chamber, whereby they are subjected to appreciable further vaporization, withdrawing non-vaporous residual liquid from the vaporizing chamber and introducing the same into a coking chamber, separating said reflux condensate into selected relatively low-boiling and high-boiling fractions, returning the high-boiling fractions to the heating coil for further conversion, subjecting the lowboiling fractions to independently controlled more severe conversion conditions in a separate heating coil, introducing the highly heated products from said separate heating coil into the coking chamber to serve as a heat carrying medium for assisting the coking operation and directing the vaporous products from said coking and vaporizing steps to the fractionator for treatment together with the conversion products from the reaction chamber.

2. A process of the character defined in claim 1 wherein the volatilized materials from the coking chamber are introduced into the vaporizing chamber to effect separation therein of the vapors and high coke-forming materials and the commingled vaporous products are directed from the vaporizing chamber to the fractionator.

3. A process of the character defined in claim 1 wherein hydrocarbon oil charging stock for the process is supplied to the first mentioned heating coil.

4. A process of the character defined in claim 1 wherein hydrocarbon oil charging stock for the process is supplied to the last mentioned heating coil.

5. A process of the character defined in claim 1 wherein hydrocarbon oil charging stock for the process is subjected in another separate heating coil to independently controlled conversion conditions of elevated temperature and superatmospheric pressure and the heated products therefrom are introduced into the separating cham ber;

'6. A process of the character defined in claim 1 wherein hydrocarbon oil charging stock for the process is separated into selected relatively highboiling and low-boiling fractions, the high-boiling fractions supplied to the first mentioned heating coil and the low-boiling fractions supplied to the last mentioned heating coil.

7. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating coil, introducing the heated oil into a separating chamber maintained under cracking conditions of temperature and pressure and separating vapors from unvaporized oil therein, subjecting the separated vaporsto continued reaction under cracking conditions of temperature and pressure and subsequently introducing the same to a fractionating zone, removing the unvaporized oil from the separating chamber and flash distilling the same by pressure reduction thereby forming additional Vapors and residue, introducing such additional vapors to the fractionating zone, distilling said residue to coke and supplying resultant vapors to the fractionating zone, fractionating the commingled vapors in the fractionating zone and separating therefrom a relatively heavy reflux condensate said heating coil, passing the lighter reflux condensate through a second heating coil and heating the same therein to higher cracking temperature than the oil in the first-named coil, discharging resultant heated products from the second coil into contact with said residue being distilled to coke to assist the coking thereof, and finally condensing and collecting the fractionated vapors.

8. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating coil, introducing the heated oil into a separating chamber maintained under cracking conditions of temperature and pressure and separating vapors from unvaporized oil therein, subjecting the separated vapors to continued reaction under cracking conditions of temperature and pressure and subsequently introducing the same to a fractionating zone, removing the unvaporized oil from the separating chamber and flash distilling the same by pressure reduction thereby forming additional vapors and residue, introducing such additional vapors to the fractionating zone, distilling said residue to coke and supplying resultant vapors to the fraction'ating'zone, fractionating the commingled vapors in the fractionating zone and separating therefrom a relatively heavy reflux condensate and a lighter reflux condensate, passing such heavy and light reflux condensate respectively through a second and a third heating coil and subjecting the same there-' in to cracking conditions of temperature and pressure, the lighter reflux condensate in the third coil being heated to than the heavy reflux condensate in the second coil, discharging the heated heavy reflux condensate from the second coil into the separating chamber, introducing the heated light reflux condensate from the third coil into contact with said residue being distilled to coke to assist the coking higher, temperature thereof, and finally condensing and collecting the fractionated vapors.

' 9. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating coil and separating the same into vapors and unvaporized oil in a separating chamber, flash distilling the unvaporized oil in a flashing zone maintained under lower'pressure than the separating chamber, removing resultant flash residue from the flashing zone and distilling the same to coke in a coking zone, passing the vapors evolved in the coking zone through the flashing zone to separate heavy coke-forming constituents therefrom, combining vapors from the flashing zone with the firstnamed vapors and fractionating the resultant mixture to form a relatively heavy reflux conde'nsate and a lighter reflux condensate, returning such heavy condensate to the heating coil,

passing the lighter condensate through a second heating coil maintained at higher cracking temperature than the flrst-named coil and then introducing the same to the coking zone, and finally condensing the fractionated vapors.

10. A conversion process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating coil, separating resultant vapors and unvaporized oil, subjecting said vapors to continued reaction under cracking conditions of temperature and pressure, flash distilling said unvaporized oil by pressure reduction in a flashing zone, removing resultant flash residue from the flashing zone and distilling the same to coke in a coking zone, passing the vapors evolved in the coking zone through theflashing zone to separate heavy coke-forming constituents therefrom, combining vapors from the flashing zone with the first-named vapors after said continued. reaction of the latter, fractionating the resultant mixture to condense heavier fractions thereof and supplying resultant reflux condensate to the heating coil, and;

finally condensing the fractionated vapors. JACOB BENJAMIN HElD. 

